Today's piston-and-cylinder engine hardware was first commercialized in the mid-18th century, using then available technology. Early internal combustion (IC) engine designers like Gottfried Daimler and Rudolf Diesel adapted the steam expansion chamber to a combined combustion and expansion chamber, leaving hardware essentially unchanged. One could say that a transformed twenty-first century embodiment of the reciprocating internal combustion (IC) engine is overdue. This disclosure focuses on improved thermal management in reciprocating devices, including pumps and IC engines. In the latter case, the improvements lead to a range of more advanced engines, ranging from modified versions of today's products, to new embodiments of reciprocating devices. In a conventional reciprocating (IC) engine, the rapid burning of the combustion charge in the confined space of the combustion volume produces expansion and heat. The expansion drives the piston and consequently engine while the heat product of the cycle is almost wholly unused—in fact considered undesirable since efforts are made to dissipate it as effectively as possible, by means of conduction through cylinder walls and head to general radiation and to the cooling system. Other heat is collected by the lubrication system to be often dissipated by oil radiators, sump cooling fins, etc. The benefits of reducing cooling to engines are substantial. Cutting down on cooling saves energy otherwise irrevocably dissipated by cooling and general radiation. It also increases the average combustion temperature, providing an additional efficiency increase, since combustion efficiency is related to the difference between firing temperature and incoming charge air, which is constant.
It is know that efficiency increases with the increase of the temperature differential of the combustion cycle. The hotter combustion, the greater the efficiency, all other factors being equal. Engine systems are designed to withstand engine performance under peak load which, in most cases occurs for a small percentage of total operating time. At all other times the engine is running colder and therefore less efficient. Today, almost all engines during most of their operating life time run at temperatures substantially below the peak temperatures they are designed for, and so at lower efficiency because of the lower temperature. To improve fuel economy and reduce CO2 emissions, a most important first step would be to maintain engine temperature at all times to be at the maximum temperature the engine can withstand, so that at all operating modes it is operating at optimum efficiency. A second step would be to eliminate the cooling system altogether and as far as possible, place the engine in a thermally insulated housing, to establish average combustion temperatures higher than previously possible. Great financial and other advantages accrue by eliminating the cost, mass, bulk, and unreliability of the cooling system. Its failure is the most frequent cause of engine breakdown. In less-cooled or un-cooled engines, the exhaust is much hotter—ie containing more energy—and more work can be derived from it, through some form of compounding, and further gains in efficiency. Turbine, steam or Stirling engines may be used to extract work from the hot exhaust gas; as can systems for converting gas heat directly into electrical energy. In an un-cooled engine, the first step described above is automatically realized, because there is little variation in temperature during different operating modes; the engine is always running close to its maximum designed temperature. Herein, un-cooled engines are described first, followed by cooled engines at all times operating at or close to maximum design temperature. Many have considered it desirable to build engines with reduced or no cooling and therefore running at higher temperatures. Efficiency would improve, since it is dependent on the difference in temperature between ambient air (which is constant) and that at combustion. The resulting hotter exhaust gases will generally be easier to cleanse. If the cooling system can be reduced or eliminated, so can some or all of its cost, mass, bulk and unreliability. Un-cooled engines can be thermally, acoustically and vibrationally insulated to virtually any degree, making them more environmentally and socially acceptable. Of the calorific value of the fuel, a greater amount will be spent on pushing a piston, but nearly all the remainder will now be in the hot exhaust gas, where it is recoverable. With the new un-cooled engines, temperature equilibria would be so high that the main piston and cylinder components would likely have to be of special high-temperature metal alloys or of ceramic material.
To the knowledge of the applicant, commercial long-life un-cooled engines are not in production today. Manufacturers and researchers tried to build un-cooled engines in the 1980's and 1990's. Publications indicate the work nearly all involved substituting or adding ceramic materials for metals in a few key combustion chamber components. For example, ceramic caps were placed on metal pistons; ceramic liners placed in metal engine blocks; a zirconia poppet valve was substituted for an identically shaped metal valve. The work was not very successful for a number of reasons, including problems with differential thermal expansion of ceramic and metal components abutting each other. Engine designs were essentially unchanged. Today's metal IC engines reflect three constraints; the materials characteristics of metals; the need for cooling and therefore the engine block, etc; and commercial practice determining the most viable ways of manufacturing and assembling metal components. The applicant felt that any viable commercial embodiment of the un-cooled ceramic engine would look very different from today's units, because all the old constraints were no longer relevant, and new constraints would apply. This disclosure includes the result of his attempt to adapt and modify the traditional design of the piston and cylinder engine, so that new embodiments could be viably built un-cooled and out of ceramic material. Many of the embodiments could also be built in high-temperature metal alloys.
The elimination of cooling will raise temperature equilibria in all part of the engine, including in the fluids being processed, leading to higher exhaust gas temperatures. In addition to having more energy to convert into further work, as noted earlier, this will have the beneficial effect of hastening the speed of the chemical reactions in exhaust gas, making exhaust emissions control systems more effective or requiring them to be less elaborate. Because exhaust emissions control is so important today, new arrangements for cleansing high temperature exhaust gases were devised, and are disclosed herein. The un-cooled engine preferably uses internal combustion cycles although, where appropriate, many principles of the invention may also be applied to, for example, engines operating on the Rankine or Stirling cycles. The engines constructed to operate continuously at maximum design temperature with reduced cooling, and those designed for life-long operation entirely un-cooled, are suitable for all applications where internal combustion engine are presently used. These include for vehicles and craft of all kinds and sizes; pumps; electrical generators; small service tools such as hand-saws, lawn mowers and trimmers, etc.
The new engines present an opportunity to create more efficient aircraft and marine craft. Compound engines including a reciprocating IC engine stage of the inventions are especially suited to hybrid electric dive systems, for aircraft and marine craft. The reciprocating engines are much lighter than current units of equivalent power and so are ideal for driving a propulsion device such as a propeller or impeller to create thrust, with the turbine stage creating additional thrust. Almost all marine craft today are hull-in-the-water vessels. It is known that hydrofoil craft are more efficient, but today's heavy marine engines do not work well in a hull suspended above water, and the hydrofoil posts present draft-related problems in larger craft. The engines of the invention are so light, silent and vibration-free that they are easily adapted to hydrofoil craft, and the hull shapes and post configurations of the invention resolve tradition problems relating to draft. Continuously variable transmissions (CVT's) are known to provide better fuel economy than traditional stepped transmissions, but today's CVT's are limited to low power applications. The transmissions of the invention are CVT's have no effective power limitation and so are very suited to larger vehicles, aircraft and marine craft.